Kuuma VF 100 not heating my house! Help!

brenndatomu

Minister of Fire
Aug 21, 2013
4,728
NE Ohio
What temperature is measured in the plenum one foot or so above the furnace if the fan is on low, fire is at maximum heat setting and full burn, and intake air is around 60.
Where at specifically? Front, side, toward the back? The front should be hotter than the back.
This may be a hail mary...but is there any chance the blower is wired wrong...as in the wrong speed taps hooked up?

 

Woodman1

Burning Hunk
Jan 15, 2018
121
Michigan
Is there a formula for measuring output from temperature rise from a forced air furnace? Something like cfm*rise?? I would think if there is it would save a lot of frustration by ruling things out. I know with a boiler it's the simple formula of gpm*500*delta t through the boiler. A quick glance at the temp gauge gives me a pretty good idea of what my boiler is doing.
 
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brenndatomu

Minister of Fire
Aug 21, 2013
4,728
NE Ohio
I think 75df register temp is the issue. Perhaps there is a ductwork issue.
Return air temp is a little low (but so is house temp) supply air is low...so register temps will be low too...but supply ducts running through a cold space is not going to help any...not sure if this basement garage is cold or not...something is off here for sure though...but I really doubt it is the furnace...my money is on something in the setup...this thing should be roasting them clean out of the house...or at least having the wife shedding layers of clothes! ;) ==c
 

hobbyheater

Minister of Fire
Nov 14, 2011
1,105
Dale said the inside flue temp should be around 225-275 and no more. I've had the barometric set every which way with nothing but cresote one way and a shorter burn the other. The cold air return is ducted right into the box. It doesn't take in hardly any basement air, I even taped it tight. I've talked to Dale and tried the baffles every which way and run the want every which way too.
Have you tried running without the barometric damper ?
 

bropp

New Member
Jan 18, 2020
16
Northern Michigan
I've tried something different this week and found an unusual result- I've had the computer on the lowest setting and it has warmed the house significantly. It got up to 65 degrees. It has been 30 out, about the same as it's been all winter. Yesterday there was a power outage and a cracked the damper open with a screwdriver. Without the fan running the house got to 67. Why would my house be so much colder with the furnace on the highest setting? I don't have it backwards and I'm not letting it burn down too much on high.
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,728
NE Ohio
Yeah, doesn't make any sense, does it?!
@JRHAWK9 found the same thing in regards to slowing the blower down heats his house better...not to the point of zero, like you had during the power outage, but still way slower than normal low speed...which is accomplished with some aftermarket controls.
As for why running the burn rate on low works better than high...you got me...unless your chimney draft is too high? That might make some sense...maybe?
Where is your draft set now? How are you checking it exactly, have any pics of that setup? I don't recall seeing where on the stove pipe you are connected in for the Dwyer...
 
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gary38532

Feeling the Heat
Nov 11, 2019
444
PA
For the last five years I've been reading great things about the vf100 and have been wanting one. I finally purchased one and am very disappointed- I can't get it to heat my house! The firebox is a blast furnace but the plenum feels cool. I don't know why the heat won't leave the firebox. I can't get my house above 60 and its in the upper 50s in the morning and it's been super warm outside- lows 20 above and highs close to thirty! I have a thermometer on the registers and usually reads 72. I don't know how to get more heat from it. I insulated the plenum and put a probe in one foot above the plenum- when the furnace is roaring on the highest setting it reads 90 degrees.

I live in a 3000 sq ft house with two garage doors in the lower level. It is essentially a 1500 sq ft ranch with a Wood walled 2x6 walkout basement. The entire thing has r19 walls. The garage doors are insulated and plugged around the edges, I don't use them. House was built in 94 and has good insulation .
I've been burning wood my entire life. I am burning dry Ash and maple between 15-20 percent on the moisture meter.
6 inch class a chimney with barometric damper. I've tried every setting on the damper and just got a Dwyer mkii to check, but think its okay as i have flue temps between 200-250. Chimney goes through a thimble and is about 25 feet tall.
I made a duct system for it- not ideal but am moving it next year. Has 10x20 trunk with 4 8 in takeoffs. I've played all around with changing the static duct pressure to increase air temp. Cold air return comes from up stairs.

The air coming out just feels cold. I've talked with Dale about a dozen times and he's been very nice, but it hasn't gotten any warmer.
My wire is furious about this whole problem and wants it returned immediately. She grew up in an uninsulated farmhouse with a hot blast that was always 80 inside even when it's -35 outside. When I go there the plenum is always HOT when it calls for heat. Mine is cold.
Help! Is the Kumma actually as good as everyone says? I really regret buying it!
This has been going on for over two months
I've tried everything
Thank god for your post so I know im not going crazy! mine is the same by all accounts... you should read my post... its long but I want to send mine back too
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
Our house is approx 3800 sq ft, 1900 up and 1900 down, tall vaulted ceilings upstairs, ~10ft ceilings downstairs. Downstairs is a walkout basement, 3 of the walls are concrete and earth-contact. Lots of cubic feet to heat, and the concrete is always trying to suck the heat out of the walls.

Here are some photos of our installation. Flue setup is similar to your. Our VF100 provides 100% of our heat down to the high-teens outdoor temp. At that point, we have to kick on the propane furnace for assist. We like to keep it 68 or above. If it's above 40 outside, I don't even fire up the Kuuma, as even on the "low" setting (and pot at low) it gets too hot inside.

Assuming the home is sealed/insulated, the Kuuma should have more than enough heat for the the OP's home. Tag to come back and read completely.

ETA: This is the first year for the return duct. The previous several years, we've just had the blower box open to the room. We added the wall for the "furnace room" last year. Knowing the room will be closed eventually, we added the return air ductwork. It feeds from the top of the furnace room wall, which is a family room.

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motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
OK, that answers one of my original questions...how long have you been using it?
Have you cleaned your heat exchanger area yet? If you had any crappy wood in that time (especially early on) it could have put a coat of crude on everything and it doesn't take much to start losing heat exchange efficiency...even with burning perfectly normally and just a light coat of fly ash on everything, I (and others) notice a difference in plenum temps vs exhaust temps right after cleaning...I try to clean 2-3 times per heating season. (you will notice exhaust temps drop, and plenum temps go up)
Hmmm...I usually clean my exchanger at the start of each heating season, and not again until the next. This is good info. If a warm day comes up where I let the fire go out, perhaps I'll check the exchanger tubes again.
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,728
NE Ohio
I usually run on the .06" side of things. Are there any benefits/reasons to lean towards the .04" side of things? Longer burn times, I suppose?
Yeah a little, but the supply plenum temps can be a bit lower too...so you either need to turn the computer up, or bump the draft up when colder weather comes.
Hmmm...I usually clean my exchanger at the start of each heating season, and not again until the next. This is good info. If a warm day comes up where I let the fire go out, perhaps I'll check the exchanger tubes again.
Not something that has to be done obviously, but for someone that is pushing the limits of the VF100, cleaning the HX every couple months (or cords) can make a bit of difference, especially right after it is done.
I'll do it if I have time during a warm spell, if not, meh...
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
Yeah a little, but the supply plenum temps can be a bit lower too...so you either need to turn the computer up, or bump the draft up when colder weather comes.

Not something that has to be done obviously, but for someone that is pushing the limits of the VF100, cleaning the HX every couple months (or cords) can make a bit of difference, especially right after it is done.
I'll do it if I have time during a warm spell, if not, meh...
Got it. We're already slightly outside the capabilities of the Kuuma, so I'll likely leave the draft where it is. I'll turn the temp knob and pot down when it's warmer out, but turn both up when it's cold. Knob all the way up, pot all the way up, everything full blast...I still have to supplement with propane once we hit the high teens ambient temps.
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,728
NE Ohio
I still have to supplement with propane once we hit the high teens ambient temps.
Still takes a huge bite out of the yearly LP bill, eh?!
The last few years were 100% wood heat here...but finally got things situated the way I want this past summer, and that allows for using some fuel oil heat when the weather is really just too warm to fool with building a small fire once every day or two. I have a small stove in the living room fireplace that can work for those warmer spring and fall days too...or if we just want some "fire TV" :)
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,728
NE Ohio
Maybe it's perspective on what we think is warm I consider 68 cold. I like to keep the house like 73-74. It's hard/almost not possible to go that high with my Kumma. In its current state it can do 68, no problem.
Agreed!
68* was the daytime setpoint when we had oil heat only...always felt cold to me...now with wood heat if we came home and found the house down to 68* it would be all hands on deck to get the fire stoked up again! ;lol
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
Agreed!
68* was the daytime setpoint when we had oil heat only...always felt cold to me...now with wood heat if we came home and found the house down to 68* it would be all hands on deck to get the fire stoked up again! ;lol
Ha! It's 71 in here now, and I'm a bit on the warm side. The few times we've accidentally got it to 73-74, the wife is complaining about it being too hot to sleep, sweating, etc. At that point we usually open some windows to cool it down a bit. Then again, 68 on propane has a different "feel" than 68 on wood. The wood heat is more comfortable.

This coming from the guy that grew up in a house that was in the 80's during winter. I remember my friends coming over to pick me up one night, and refusing to come in because it was in the 90s. Middle of winter, and we'd be running around the house shirtless in our tightly whiteys, with front and back door open...
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
Still takes a huge bite out of the yearly LP bill, eh?!
Certainly! The house came with a small Avalon Arbor (same as Lopi Leti, I believe) EPA stove. The 2nd year in the house, we used this stove to burn some trees I had cleared on the property. This little stove was rated for something like 2k sq feet...approx 1/2 the size of the house. We were AMAZED at the reduction in propane usage, as well as the increased comfort in the upstairs (tile) floor...due to the heat rising from below.

The things we learned with Avalon played a part in the decision to drop the "big bucks" on the Kuuma.
 
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brenndatomu

Minister of Fire
Aug 21, 2013
4,728
NE Ohio

Spanky

Member
Jan 5, 2017
6
Dexter, Michigan
Hard to believe that your basement doesn't heat up from that Kuuma. We have had ours 4 years now. Home is a
1700 sq ft ranch built in 77. We have a walkout type garage in the basement where I located the furnace. Basement walls
are cinder block in that area. Zero insulation. My temps run consistently above 80 degrees in the basement. I have never had to turn the computer setting above low since I have run the furnace. Our temps are almost always 68 to 71. Any
warmer and the wife starts disrobing. Lol. Just love the furnace and really try to have a good supply of dry wood.
 

gary38532

Feeling the Heat
Nov 11, 2019
444
PA
Hard to believe that your basement doesn't heat up from that Kuuma. We have had ours 4 years now. Home is a
1700 sq ft ranch built in 77. We have a walkout type garage in the basement where I located the furnace. Basement walls
are cinder block in that area. Zero insulation. My temps run consistently above 80 degrees in the basement. I have never had to turn the computer setting above low since I have run the furnace. Our temps are almost always 68 to 71. Any
warmer and the wife starts disrobing. Lol. Just love the furnace and really try to have a good supply of dry wood.
so wait? its warmer in your basement then upstairs...